Arduino relay board distance limitations

Hi

I wouldn't opt for either  of these two methods although they may work when you running fairly long distances  I would personally  consider  using RS485  as the protocol to communicate btw smaller devices and processors  a cheaper method  more reliable method of doing this

If you were considering wireless communications you would be far better with physical hardware connections  Its far more reliable than esp8266 at present although this implements a full tcp ip stack you have to consider that you would be using UDP over cat 5  which is the useless datagram protocol as some correctly  describe this as Restful services with json integrating serial port applications using client server technology via web page interface  might be another option but agin unless you've spent some time with this It is unfortunately a question of time  with very in depth theory required

A much stronger alternative is often described as the DCI Bus

The idea of using an op-to coupler is  good design but id apply this to  each receiver  on the output side which sits on your multi-point Rs485 design to drive your relays rather than your input side

That way you can have each microchip addressable

Ideally my suggestion would be to use a master and slave routine on this with the master controller sending out your serial packets which contain destination address op code and CRC checksum with an ack once your relay has been activated 

Hence you then also  have some form of fault diagnosis  in other words has the relay been actuated via ack

Here is some more info on rs485  with schematics for you to study and implement in your design  https://www.dcisite.be/dcibus.html

When producing your final relay driver board and micro receiver on each be very careful about track spacing and also induced RF via the relay coil Ive found this to be quite a problem on previous designs so good decoupling is needed as well as reverse emf protection to prevent destruction of relay driver stage and also upsetting the ports of the cpu

Thats the best advice I can provide based on practical designs that Ive produced myself

For further reading on the RS485 interface please see the following

RS485, specifications and in depth tutorial

I wish you luck with your project

Mark Harrington

Hi

I wouldn't opt for either  of these two methods although they may work when you running fairly long distances  I would personally  consider  using RS485  as the protocol to communicate btw smaller devices and processors  a cheaper method  more reliable method of doing this

If you were considering wireless communications you would be far better with physical hardware connections  Its far more reliable than esp8266 at present although this implements a full tcp ip stack you have to consider that you would be using UDP over cat 5  which is the useless datagram protocol as some correctly  describe this as Restful services with json integrating serial port applications using client server technology via web page interface  might be another option but agin unless you've spent some time with this It is unfortunately a question of time  with very in depth theory required

A much stronger alternative is often described as the DCI Bus

The idea of using an op-to coupler is  good design but id apply this to  each receiver  on the output side which sits on your multi-point Rs485 design to drive your relays rather than your input side

That way you can have each microchip addressable

Ideally my suggestion would be to use a master and slave routine on this with the master controller sending out your serial packets which contain destination address op code and CRC checksum with an ack once your relay has been activated 

Hence you then also  have some form of fault diagnosis  in other words has the relay been actuated via ack

Here is some more info on rs485  with schematics for you to study and implement in your design  https://www.dcisite.be/dcibus.html

When producing your final relay driver board and micro receiver on each be very careful about track spacing and also induced RF via the relay coil Ive found this to be quite a problem on previous designs so good decoupling is needed as well as reverse emf protection to prevent destruction of relay driver stage and also upsetting the ports of the cpu

Thats the best advice I can provide based on practical designs that Ive produced myself

For further reading on the RS485 interface please see the following

RS485, specifications and in depth tutorial

I wish you luck with your project

Mark Harrington